1. Field of the Invention
The present invention relates to a shuttle for ribbon looms.
2. Prior Art
One known expedient for keeping the thread from the shuttle bobbin under tension is a leaf spring held in frictional contact with the circumference of the bobbin which is mounted for rotation on a spindle in the shuttle housing. As the thread is unwound from the bobbin, the bobbin decreases in diameter and becomes lighter in weight, with the result that the force with which the leaf spring is pressed against the bobbin gets weaker gradually. With this type of tensioning device, therefore, the thread cannot be tensioned constantly throughout its entire length. Furthermore, the tension of the thread varies with the position at which the thread unwinds off the bobbin. The resultant woven fabrics are liable to have the irregular selvages and to become greater in width as they are being progressively produced.
Another problem with prior shuttle structures is that since the shuttle reciprocates along a substantially arcuate path through the successively formed warp shed, and the shuttle has a thread discharge eyelet in its front frame, a length of the thread after emerging from the shuttle and before being interwoven changes at all times; that is, it continues to become shorter until the shuttle enters the warp shed, and starts getting longer with the movement of the shuttle across the warp shed. Therefore, the thread is subjected to fluctuating tension upon departure from the shuttle. A pair of coil springs are disposed within the shuttle housing in order to take up the slackened thread or stabilize its tension, but are unable to follow the continuously changing tension of the thread because of high speed operation of the shuttle.